This application claims the benefit of German patent application No. DE 10019734.5 filed Apr. 20, 2000, and German patent application No. DE 10033015.0 filed Jul. 6, 2000, herein incorporated by reference.
The present invention relates to a method for producing a cheese which provides for utilizing a predetermined placement distance and controlling the crossing angle and the winding ratio as a function of the cheese diameter, whereby the winding ratio is reduced and the placement distance is increased with an increase in the cheese diameter. The present invention further relates to a cheese so produced having yarn windings arranged so that the crossing angle and the winding ratio are reduced with increasing diameter of the cheese.
Cheeses can be produced with random windings, precision windings or progressive precision windings. These types of windings are extensively described, for example, in European Patent Publication EP 0 486 896 B1 or German Patent Publication DE 42 23 271 C1 or in the older, not prepublished German Patent Application DE 100 15 933.
In European Patent Publication EP 0 486 896 B1, winding the yarn is performed by progressive precision winding. In the process of progressive precision winding, the winding is built up in several steps. The frequency of cross winding is reduced in each individual step proportionally with the number of revolutions of the bobbin. Once the smallest, still permissible placement angle has been reached, the cross-winding frequency is suddenly increased. Because of the sudden increase, a new, smaller winding ratio arises. This process is repeated until the predetermined bobbin diameter has been achieved. During winding, the yarn is deposited while taking a placement distance into consideration, wherein it is intended to keep the placement distance as small as possible. Under special conditions, such as, for example where noticeable effects on the position of the windings of the yarn occur in the course of placing the yarn due to changes in tolerances or play in the drive mechanism of the winding device, it is recommended to select a placement distance which is not overly narrow. The placement distance preferably corresponds to the yarn width or the yarn diameter. Pursuant to this method, the predetermined placement distance always remains the same once it is selected.
German Patent Publication DE 42 23 271 C1 also describes the creation of cheeses by means of a progressive precision winding. As in European Patent Publication EP 0 486 896 B1, the selected, predetermined placement distance is intended to be as small as possible and also remains constant.
Both of the publications referenced above relate to methods for avoiding working with xe2x80x9cdangerous mirror pattern valuesxe2x80x9d in which the yarn lies on top of itself from one layer to layer and the disadvantages during bobbin building associated therewith.
German Patent Publication DE 40 24 218 A1 is representative of the state of the art and discloses a method for controlling the cross-winding speed during the production of a cheese so that the crossing angle changes at least approximately steadily as a function of the bobbin diameter from a selectable value in the first yarn layer to a selectable final value in the last yarn layer, and that simultaneously, the winding ratio or spooling ratio, also changes at least approximately steadily from an initial value in the first yarn layer to an end value in the last yarn layer. As in the random winding method, the method includes a steady change of the winding ratio. However, in contrast to the random winding method, the amount of the change of the winding ratio is freely selectable or controllable with a steady change of the crossing angle. In accordance with this method, a whole-number winding ratio, and therefore the appearance of the disadvantageous winding patterns or mirror patterns associated therewith, is intended to be either avoided or rapidly passed through.
Further, not prepublished German patent application DE 100 15 933 describes a method for controlling the crossing angle and the winding ratio so that it is possible to achieve an excellent unwinding behavior of the cheese. During the production process of the cheese, there are a number of requirements, such as flat front faces or maintaining a constant winding tension, which are desirable. However, in order to meet these requirements without impairing the stability or desired shape of the cheese due to blooming, it is necessary control the crossing angle and the winding ratio within narrow limits. Thus, a large outlay in equipment and controls, such as, the employment of a winding tension control, must be provided.
In order to prevent deformations in the edge area or of the front face of the cheese, it is typical to permit a bobbin build-up at the edge having a slightly conical shaped front face. It is known to create this conical shape by the axial extension of the winding of the cheese, which decreases with increasing bobbin diameter and is hereinafter referred to as xe2x80x9cbobbin traversexe2x80x9d. With increasing bobbin diameters, the bobbin traverse is affected in that the distance between the clamping line and the yarn guide becomes greater, and thus, the reversing points during the placement of the yarn wander inward thereby causing the reduction of the bobbin traverse when the bobbin diameter increases. While a cheese production process resulting in slightly conical front faces helps to prevent deformations of the cheese, there are disadvantages in stacking and transporting finished cheeses with slightly conical front faces. During stacking and transporting, the cheeses are typically set up so that their axes of rotation are in a vertical position and the yarn bodies must support the weight of the pallets located on top of them. Therefore, while the conical shape of the front faces may be acceptable, or even actively created, for the reasons set forth above, the conical shape of the front faces clearly limits the options, or the load-bearing capability of the cheeses, during stacking and transport of the pallets. It is also very disadvantageous that an increasingly conical shape of the front face, or a trapeze-shaped cross section, of the cheese is present in conjunction with a reduction of the bobbin volume, or of the yarn body thereby resulting in a considerable reduction in the running length of the bobbin.
Moreover, blooming can occur in spite of conically shaped front faces, particularly with cheeses of large diameters, for example, cheeses having diameters of more than 300 mm. While it is possible to counter blooming during constantly maintained winding tension by increasing the crossing angle, such action causes the bobbin traverse to become even smaller and further reduces the bobbin volume. Alternatively, blooming can be counteracted by lowering the winding tension. However, in cases where paraffin is applied to the yarn, it is known that a constant winding tension is a prerequisite for a uniform paraffin application to the yarn. Thus, the lowering of the winding tension, at least in connection with cases where paraffin must be applied, does not represent a satisfactory solution. Further, reducing the winding tension in the manner performed in accordance with the known prior art can lead to the winding tension in cheeses with large diameters to become so low at the end of the bobbin travel, that tangled, or unstable layers are created. However, if the winding tension is appropriately increased at the start of the bobbin travel in order to prevent the reduction to too small winding tension, the danger of too high a winding tension at the start of the bobbin travel exists. In any case, the winding tension is not uniform.
When drawing the yarn off feeder rolls in a constant manner, such as is the case during open-end spinning, a decreasing bobbin traverse leads to a reduction of the winding tension when the bobbin diameter is increased. Therefore, the constant winding tension required for uniform paraffin application to the spun yarn is no longer met. A constant winding tension can be achieved again by reducing the crossing angle as the bobbin diameter increases. Although it is possible to maintain the winding tension and the achieve a substantially uniform paraffin application in this manner, deformations of the cheese will likely result due to the reduction of the crossing angle.
Thus, while a reduction of the crossing angle is employed in connection with the known prior art in rigid placement systems, i.e. at a constant cross-winding traverse of the yarn guide, in order to maintain the desired bobbin traverse, there are disadvantages, as discussed above, associated with employing such a reduction.
It is an object of the present invention to overcome the disadvantages described above by providing an improved method for the production of cheeses and a cheese so produced.
In accordance with the present invention, an improved method for producing a cheese is provided for a cheese having a yarn body and being rotational around its longitudinal axis in which the yarn is subjected to a cross-winding movement while being fed to the cheese and wound thereon, and whereby the winding process includes a crossing angle and a winding angle associated therewith. More particularly, the method includes determining a placement distance, controlling the crossing angle and the winding ratio as a function of the cheese diameter wherein the winding ratio is reduced as the cheese diameter is increased, and controlling the placement distance so that the placement distance increases as the cheese diameter increases.
By applying the method of the present invention which provides for controlling the placement distance so that it increases with increasing cheese diameter, the conicity of the front faces of the cheese can be advantageously reduced or eliminated without blooming or similar disadvantages occurring, and without the necessity of an additional large outlay in equipment.
In the method of the present invention, the density of the yarn body of the cheese is preferably reduced as the bobbin diameter is increased. Thus, the present invention effectively prevents the pressure on the inner layers of the cheese from becoming so strong that deformations of the cheese occur.
A preferred embodiment provides for the density of the yarn body to be matched to a predetermined progression of the density values over the cheese diameter. Matching is performed by a correspondingly controlled change of the placement distance. During the matching process, an allocation of the crossing angle, the density value and the placement distances takes place. Through such allocation, a simple and effective control becomes possible.
In accordance with the method of the present invention, the drive of the cheese and the cross-winding movement are actuated by drive elements which can be separately adjusted.
Preferably, the crossing angle is controlled so that it is reduced as the cheese diameter is increased and the placement distance is increased in accordance with the present invention, thereby producing a cheese with flat front faces by means of a reduction of the crossing angle, without increasing the pressure on the inner layers of the cheese. Because the reduction of the crossing angle in this manner does not increase the pressure on the inner layers of cheese, the deformations, or blooming, particularly at the front face of the cheese, typically caused by a reduction of the crossing angle are avoided. Utilizing the method of the present invention, improved cheeses can be produced on winding heads which are operated at open-end spinning frames with constant yarn draw-off. The volume of the cheese, as well as the running length, are advantageously increased by flat front faces. Thus, the present invention provides a method for preventing the decrease of the bobbin traverse and reduction of the accompanying winding tension which utilizes a reduction of the crossing angle whereby the winding tension is kept substantially constant and thereby permitting uniform paraffin application to the yarn.
The present invention advantageously provides for the reduction of the crossing angle utilizing a rigid placement system for generating the cross-winding movement of the yarn, such as, by way of example, a reverse yarn guide whereby the bobbin traverse can be maintained in the desired amount without causing deformations, or blooming, of the cheese.
In the method of the present invention, the determination of the placement distance is readily calculated by means of the following mathematical equation:
s=dv+E0+f(D), 
wherein
s=placement distance
dv=preset yarn diameter
E0=base value for the free space between two yarn windings deposited at the placement distance
f(D)=a value depending on the diameter of the cheese.
In addition, the following mathematical equation is used to include possible fluctuations of the yarn diameter:       s    n    =                              d          n                +                  d          nw                    2        +          E      n      
The following applies for En: 
En=E0+bxc3x97(Dxe2x88x92D0), 
wherein:
sn=placement distance after the nth winding
dn=yarn diameter of the nth winding
dnw=yarn diameter of the yarn winding placed at the placement distance sn after the nth winding
E0=base value for the free space between two yarn windings deposited at the placement distance
En=free space between the yarn windings of the nth winding and the following winding
b=factor to be established
D=diameter of the cheese
D0=diameter of the bobbin case
In a variation of the method of the present invention, values stored in the form of tables in a data memory are used to establish the progression of the density values, as well as the determination of the placement distance. In use, the stored data may be empirically determined, or may represent experimental values.
A precise measurement of the density of the yarn body of the cheese may be calculated by means of a control, wherein the actual yarn diameter is measured and the calculation of the actual placement distance is performed so that the effect of the fluctuations of the yarn diameter on the free space between the windings of the yarn is compensated.
The method in accordance with the present invention readily provides for the maintenance of the winding tension within narrow tolerances which permits a substantially uniform paraffin application to the yarn while simultaneously permitting the lateral surfaced to extend substantially perpendicularly to the axis of rotation without a danger of deformation in bobbin building. Thus, the present invention advantageously increases the volume and the running length of the cheese.
In addition, the present invention provides further advantages in stacking and during transporting the finished cheeses. Specifically, the useful support surface of cheese produced or built in accordance with the present invention is improved because the lateral surface is substantially flat thereby increasing the load-bearing capability and stability of a transport arrangement consisting of pallets equipped with such cheeses.
Further details, features and advantages of the present invention will be disclosed in and understood from the following disclosure of one or more preferred embodiments of the present invention with reference to the accompanying drawings.